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International Journal of Anatomical Variations (2009) 2: 91–92
eISSN 1308-4038
Case Report
Variations of the proximal attachment of the biceps brachii muscle in a Nigerian population
Published online August 19th, 2009 © http://www.ijav.org
Anyanwu Godson EMEKA
Obikili Nebeuwa EMMANUEL
Department of Human Anatomy, College of Medicine, University of Nigeria, Enugu
Campus, Enugu, NIGERIA.
ABSTRACT
Various types of variations have been associated with the proximal attachment of the biceps brachii muscle
(BBM). The bulk of the reports, been studies done on Caucasian subjects. This is a case report on the
supernumerary and variant heads of the proximal part of BBM in three young male adult Nigerian cadavers.
Supernumerary occurrence of the head of BBM noted was that of 3 heads and this occurred unilaterally.
Another variation noted in another subject was that of the origin of the short head of biceps brachii (SHB)
from the acromion and from the supraglenoid tubercle, which also occurred unilaterally. These findings were
compared with other documented reports. © IJAV. 2009; 2: 91–92.
Anyanwu Godson Emeka, PhD
Department of Human Anatomy
Faculty Of Medical Sciences
College of Medicine
University of Nigeria
Enugu Campus, Enugu State, NIGERIA.
+234 803 6765433
[email protected]
Received April 4th, 2009; accepted June 23rd, 2009
Key words [gross anatomy] [variations] [biceps brachii] [supernumerary head]
Introduction
Biceps brachii muscle (BBM) is one of the most variable
muscles in the human body, in terms of number and
morphology [1,2]. It normally originates from two heads;
the long and the short heads. Various forms of variations
with differing prevalence have been noted in the various
reports on various races and ethnicities. Amongst the
supernumerary heads of BBM reported is the presence
of 3 to 7 heads [1-4]. The absence of the long or the short
head of BBM [1], and variation in its insertions [5,6],
have also been reported. In literature, the prevalence
of supernumerary heads of biceps ranges from 9.1% to
22.9% [7,8].
In this case report, we report the variations of the
proximal attachment of BBM in three Nigerian subjects,
and also compare the findings with previous studies.
Case Report
During a supervised dissection of 3 adult male formalin
fixed Nigerian cadavers by the medical students of the
Department of Anatomy University of Nigeria, some
variations in the proximal attachment of the BBM
were noted. The dissection procedure was as directed
in Cunningham’s Manual for dissection [9]. Further
dissections were carried out by the authors and the
variations were photographed and documented.
In the first two cadavers, a supernumerary occurrence
of the heads of BBM was noted. The supernumerary
occurrence in this study was in the form of the third
head. In both cases the occurrence was unilateral; the
third head was lying between the long and short heads.
On both occasions, the third head was running within the
capsule of the shoulder joint along the bicipital groove
to pick origin from the supraglenoid tubercle of the
humerus (Figure 1).
In the third cadaver, the variation was on the origin of
the short head of BBM: from the acromion and also the
supraglenoid tubercle. This gave a picture of a short head
of BBM having two heads, as superficial and deep. The
superficial head extending to the supraglenoid tubercle
1
3
2
4
5
6
Figure 1.  The photograph of the third head of the biceps brachii. (1:
pectoralis minor; 2: coracobrachialis; 3: short head of biceps brachii;
4: third head of biceps brachii; 5: long head of biceps brachii; 6: cut
edge of pectoralis major)
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Anyanwu and Obikili
was running medial and slightly deep to the long head
of biceps. The deep head was running obliquely medial
to the superficial head and lateral to the tendon of
the coracobrachialis. After fusing with the tendon of
coracobrachialis, it extended to the coracoid process and
attached to it. This attachment extended posteriorly to
the acromion of scapula via a ligamentous extension
(Figure 2).
Discussion
Among the reports of the various studies on the origin of
the BBM, the occurrence of supernumerary head has been
the most prevalent variation. Within numerous reported
cases of supernumerary heads of BBM, the third head
of BBM was the most common [4]. Within the reported
prevalence range of 9.1% to 22.9% of the supernumerary
head of BBM [4], a prevalence range of 7.5% to 18.3%
has been reported for the third head of BBM.
In agreement with the reports of Kosugi et al. [4], and
Nakatami et al. [2] on the rarity of the bilateral occurrence
of the supernumerary heads of this muscle, in our report
we did not note bilateral occurrence in the sampled
population. Kosugi et al. [4] and Asvat et al. [10] stated
that there are no clear gender and racial differences in
the occurrence of the supernumerary head of the biceps.
The documented variant origins of the short head of
BBM from the acromion and supraglenoid tubercle are
rare cases that have not been documented in literature
yet. The extension of the origin of BBM to the acromion
is a feature that will add more stability to the shoulder
joint. It will also add an undue force to the protraction
of the scapula during contraction of this muscle, thereby
making this variation very beneficial for people interested
in activities such as boxing.
1
2
3
5
4
7
6
8
9
Figure 2.  The photograph of the variant origin of the short head of
biceps brachii. (1: acromion; 2: ligamentous extension of the short head
of biceps brachii to the acromion; 3: coracoid process; 4: pectoralis
minor; 5: long head of biceps brachii; 6: tendon of the short head of
biceps brachii to the supraglenoid tubercle, 7: tendon of the short
head of biceps brachii running to fuse with that of coracobrachialis;
8: reflected head of pectoralis major; 9: coracobrachialis)
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